Seattle Weather Averages

Seattle, Washington is a city of wet winters and dry summers. The moderate year-round temperatures mean that Seattle rarely sees snow, and yet the city enjoys pleasant summers.

This page gives detailed information on the annual weather averages for Seattle.

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The temperature, precipitation and sunshine numbers here are historical averages based on climate data gathered at Seattle's Husky Stadium, located near downtown Seattle at the University of Washington on the shore of Lake Washington's Union Bay. The rest of the measurements are averages from the Seattle - Tacoma International Airport, located south of the city center.

Temperature Weather iconTemperature

61 °F annual average high 16 °C
46 °F annual average low 8 °C

Seattle's coldest days of the year usually occur in mid December when the daily maximum temperature averages 46 degrees Fahrenheit (8 degrees Celsius) and the minimum averages 36 °F (2 °C).

The year's hottest days are normally at the end of July and beginning of August. The average temperature peaks then with daily highs of 77 °F (25 °C) and nighttime lows of 58 °F (14 °C).

93 days 70 °F max. or more (21 °C)
99 days 40 °F min. or less (4 °C)

Seattle averages 24 days a year when the thermometer reaches into the 80s °F (over 27 °C). The temperature typically climbs to 90 °F (32 °C) on just one or two days a year. Days as hot as 100 °F (38 °C) are not normal for the city.

Nearly every day in Seattle is at least as warm as 40 °F (4 °C). Only once a year on average does the temperature remain below freezing for the entire day.

The thermometer dips to freezing or below on 23 nights each year. Seattle normally gets as chilly as 20 °F (-8 °C) once or twice a year.

Rainy Weather iconPrecipitation

37.7 in total precipitation 958 mm
149 days of rain or snowfall

December is usually the wettest month of the year in Seattle, while July and August are the driest.

Snowy Weather iconSnow

5.0 in total snowfall 12.7 cm
3 days with new snow

Snow can fall in Seattle during any month from November to March. But more often than not for any individual month the city sees no snow. Seattle averages just one day a year when the snow covering the ground accumulates to 5 inches (13 cm) or more.

Sunny Weather iconSun

43 % sunshine
71 days clear skies

The sun's rays reach the ground in Seattle during 43 percent of daylight hours on average year round, for a total of 1922 hours annually. Typically on 71 days a year the sky is mainly clear, with at most 30 percent cloud cover.

Sunlight in Seattle averages 12 hours and 14 minutes a day. The shortest days of the year in mid December have 8 hours and 25 minutes of daylight. The year's longest days in mid June last 15:59 from sunrise to sunset.

Humid Weather iconHumidity

73 % average humidity

The annual average for relative humidity in Seattle ranges throughout the day from 83 percent at 4:00 am to 62 percent at 4:00 pm standard time.

Local Time1 am4 am7 am10 am1 pm4 pm7 pm10 pm
Humidity % 80 83 82 73 64 62 68 75

Windy Weather iconWind

8.8 mph wind speed average 14.2 kph

January and December are usually the windiest months for Seattle, while the wind is calmest during August.

Stormy Weather iconStorms

5 days precipitation of 1 inch (25 mm) or more
1 day snowfall of 3 inches (8 cm) or more
7 days with thunderstorms a year

Heavy rainstorms are mainly a winter event, most commonly arriving during November to January.

Seattle is most likely to get a heavy snowstorm during December. About once a decade the city gets a snow dump of 10 inches (25 cm) or more in a single day.

Thunderstorms most commonly appear over Seattle during April and July, although they can arrive during any month.

Reference

These weather data are long-term historical averages provided by the National Climatic Data Center of the United States. The temperature and precipitation numbers are 1981-2010 normals while the humidity and thunderstorm statistics are 1961-1990 normals.

Seattle Weather
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